Edumuhcate me on AR9's / 9mm AR pistols

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#operator

Possibly looking into putting together a 9mm AR style pistol. All I know is that you can do either Glock (no thanks) or MP5 (yes please) style mags. I've seen lowers from NFA and one other - possibly C5?

Whats a good length for reliability on the barrel?
What other choices are there for lowers?
Im assuming since it's an AR style rifle uppers and lowers match regardless of brand?

uber Member

The only answers I know from my own research is that all 9mm uppers do not work if you're wanting MP5 mags as the mag geometry is different. That being said there is a third option which is ones that take the Colt stick mags which is less ugly than the glock mags but not quite as cool as the MP5 mags. There is also the last option of conversion blocks that allow you to use Colt or Uzi mags in a standard AR lower, which equates to a way to get your feet wet without fully committing to a 9mm lower, but tbh at the price they cost you may as well drop the extra 100 bucks on an actual lower.

Worktruck Driver

I can only speak to what I built but the matching upper to the C5 works well. I personally wouldn't mix and match receivers, part OCD part want of reliability. QC10 are highly regarded, think Noveske for 9mm pistol caliber carbines. You'll want a dedicated 9mm bcg. From all my reading over on AR15.com, buffer weight seems to be a variable to reliability. I'm still early days with mine but factory ammo has worked well. My 115gr reloads need tweaking but the 147gr HST reloads have been ok for the few that I have shot.

I aim to misbehave...

Is the extra heft of a full AR platform worth it in a 9mm? There are a lot if nice 9mm carbines that are purpose built and don’t come with the glitchy hiccups of trying to stuff 9mm into a bloated platform. I strongly considered it for my AR pistol build years back but went against it. Options like the Sub-2000 are only 29.5” long which is the same length of a 10” barreled 9mm pistol (and you get an extra 6” of barrel on the S2K).

LEGEN...wait for it... DARY!

Best reason would be having the same manual-of-arms between your 9mm carbine and your .223 varmint carbine.

When it comes to the Sub-2000, I learned the hard way that the grip is shorter than the Glock model it shares magazines with, probably because the magazine goes further up into the action. A Sub-2000 that uses Glock 19 magazines (the one I bought) has the annoyingly short grip similar to a Glock 26. If I were to do that again (no need (then or now)) I would get the Glock 17 style of Sub-2000 and then modify the grip on the sides and front to accept the shorter Glock 19 magazines but still have some meat on the back for comfort. Or, use Glock 17 magazines in the carbine and pistol, and realize that Glock 19 magazines won't work in the carbine. Something to know ahead of time when choosing one.

Worktruck Driver

I think my setup is just under 6lbs unloaded. There are plenty of people running AR9's now that finding a setup that works should be easy enough with some research. Manual of arms plus the option of building, something I like, were considerations. While I would love to have a semi auto MP5 or clone, they are still in the $1500 range for a decent one. More than I wanted to pay for sure and building one with the NFA receiver set was a little less than half that.

I aim to misbehave...

Zombies aren't real

My perusing of the interwebz lead me to opt for an 8.5" barrel as the sole purpose behind my wanting a 9mm AR pistol is as a host for my AAC Ti-Rant 9M I've been waiting on approval for. I know that the bolt for Uzi style mags and Glock mags are different though I'm not certain about bolts for MP5 mags.

My lower is a NFA C-9 and the PSA LPK that comes with the SBA3 brace. I originally wanted to build my upper but bought a complete Foxtrot Mike Products 8.5" upper for $385.99 shipped from Brownell's (FM-9 Complete Upper). It is a slick side upper receiver with a non-reciprocating side charging handle and I've found that the handle is a good substitute for a finger stop though it's more of a webbing between your thumb and index finger stop. The fit is absolutely perfect and I had no need for any modifications to it whatsoever. My total cost was $720 as I had a Bushnell TRS-25 lying around that I put on it. You cannot go wrong with the C-5 if you want to use MP5 magazines. I find the C-5 to be more pleasing to the eye with a magazine in it however I have way too many Glock mags as is and MP5 mags aren't cheap.

LEGEN...wait for it... DARY!

Never been a fan of the MP5 design, but I'd rock a G3 (HK91, PTR-91, etc) battle rifle if I needed to. Get them both and you are back to the same manual of arms again. If you prefer varmint rifles instead of battle rifles, there's always the HK93 variant.

#operator

Never been a fan of the MP5 design, but I'd rock a G3 (HK91, PTR-91, etc) battle rifle if I needed to. Get them both and you are back to the same manual of arms again. If you prefer varmint rifles instead of battle rifles, there's always the HK93 variant.

Honestly, I have a lot of firearms that I shoot that are "purposeful," Some that just sit in the safe and there are others I want simply because they are cool. I just think the MP5 is cool as hell. It could be a terrible design for all I know.